Mr. Mashburn believes people should be happy. And he's doing his best to have them leave his bus with a smile. "You come in here with a bad attitude, guess what? You leave here with a better frame of mind," he says. "If I'm happy, I want everybody else to be happy."

Happy New Yorkers? Happy Americans? Indeed, happiness appears to be making a comeback as the country bids goodbye to a century marked by its share of angst, uncertainty, and The Jerry Springer Show.

What appears to be a grass-roots "happiness movement" is sprouting on the Internet - with dozens of Web sites dedicated to "happiness and well-being." Politicians are pledging to go positive. And many advertisers are going upbeat, eschewing the starved heroin-chic look for wholesome, healthy models cavorting in meadows.

"I really do believe we're approaching a new paradigm," says Michael Lonergan, creator of the www.happyplace.net and a retired Pace University professor in New York. "We've so trivialized happiness that it's begun to mean nothing, but many are now saying, 'Why am I waiting for happiness, why is it something that's off in the future? It's something that should be here, right now.'"

The scientific study of happiness is also taking off with researchers around the world trying to understand just what it is that makes us content and brings a smile. But is this a fad, or a fundamental shift underlying the American psyche?

Looking on the bright side

One of the first things social scientists will tell you is that Americans are overall pretty happy - at least on the surface.

According to the National Opinion Research Center (NORC) at the University of Chicago, an average of 32 percent of Americans have consistently reported being "very happy" since 1972. About 56 percent report being "pretty happy." That leaves only about 12 percent who report being "not so happy." Those numbers have varied only slightly since 1957, when NORC started tracking the American mood.

"The present is just like the past," says Tom Smith, director of the General Social Surveys at NORC.

Or is it? That depends on how you define happiness.

In the post World War II era, happiness was heavily weighted toward economic security and financial success. That's changed in the last 25 years, according to researchers, toward being increasingly concerned with quality of life - from environmental protection to a greater concern for the quality of human relationships.

David Myers, author of "The Pursuit of Happiness," says that the average American's personal disposable income has doubled since the 1950s from $8,000 to $20,000 in constant dollars.

Americans have twice as many cars per person, and eat out more than twice as often. "The point is, we're more than twice as rich and no happier so that economic growth has been associated with no advancement in human morale," he says.

That comes as no surprise to Ronald Inglehart. He's researched "subjective well being" in more than 60 countries. In very poor ones, those with average per capita incomes of less than $7,000, he's found a strong and direct correlation between economic development and happiness. The more money those in very poor countries have, the happier they are.

There is a big jump in the contentment quotient between Bangladesh and Spain. But among the Western industrialized nations there's little or no correlation at all between income and happiness.

"The Irish show a higher level of subjective well-being than the West Germans, even though [the Germans] are twice as rich," Mr. Inglehart points out. "And the South Koreans show subjective well being levels as high as the Japanese, even though the Japanese are four times as rich."

In the United States, there is a slight correlation between income and sense of well being, at least above the poverty level.

Bill Gates might be several million times as rich as most Americans but he might at best be 1 percent happier, says Inglehart. That's a reflection in part of the fundamental shift in the way Americans define happiness.

Pam Johnson started the "Secret Society of Happy People" in part as a sort of tongue-in-cheek idea about a year ago. She was tired of people always "raining on her parade." So she designed a Web site and started chatting with people who were also tired of what seems like the constant negativity in American culture.

"We're bombarded by bad news 24 hours a day, seven days a week," says Ms. Johnson, who lives outside Dallas. "Sometimes the bad-news moment doesn't have any more impact on people's lives than the good-news moment."

Johnson says that maybe people are just as happy now as in the past, but they don't talk about it as much, it's not chic. But she also believes that's changing. The Society now has had over 130,000 hits on its Web site since December. She even asked all 50 governors to declare Aug. 8 National Admit You're Happy Day. The responses were mixed.

Don't worry, be happy

But Madison Avenue, that great barometer of the American frame of mind, has already starting tapping the country's upbeat mood.

"There's a lot of feel-good advertising out there - the Gap ads, the Taco Bell dog, the Apple MacIntosh - that's working well for those brands," says Carol Costello of TBWA/Chiat/Day Advertising in New York. "Americans are in a good mood, and I think the happiness trend will continue."

But bus driver Mashburn doesn't see it as only a trend. It's a state of mind. "It's something that you decide," he says. "If you want to be happy, you can. It's how you look at the world, and what you do in it."